1. Field of the Invention
The present application relates to acoustic emission contact fuzes for missiles and, more particularly, to an acoustic emission contact fuze with signal processing capabilities.
2. Description of the Prior Art
Piezoelectric contact fuzes are well known in the art. The fuzes presently in use are sensitive only to direct impacts and are not sensitive to glancing blows or contact where only a portion of the missile is involved.
The conventional methods used to increase the sensitivity to glancing blows are such means as wires on the outside surfaces of the fins, or accelerometers of increased sensitivity. The wires are separated from fin structure surface by a thin layer of a crushable insulator. Upon an impact with a target a short circuit is created which triggers a detonator. The fragility of this system requires extra precautions in the shipping and handling of the missiles such as the use of fin guards. In addition, a check must be made of damage to the structure immediately prior to firing.
Accelerometers consisting of a piezoelectric material with a mass attached have also been used. Increasing the sensitivity of the accelerometer can provide some reaction to glancing blows. As the sensitivity is increased however, environmental factors can lead to false contact signals.
It has been proposed that a fuze could be constructed by placing a piezoelectric transducer on the structural elements of the missile linked to the fin structure. When an impact occurs with the fin structure the supporting structure would be deformed. Deformation of the structure would bend the piezoelectric crystal causing an electrical signal which could be detected. The signals then could be used to trigger the warhead. Previously such attempts have been unsuccessful due to sensitivity to normal vibration or motor-chuffing in flight. These prior configurations have been limited to stress waves of a frequency below that utilized by the claimed invention.
Major disadvantages of present techniques are insensitivity to glancing blows and/or sensitivity to flight environmental conditions and the requirement of extra handling precautions.